Several desirable attributes for a probe tip include, but are not limited to: an adequate level of structural robustness, a small apex cross-section-to-tip-height ratio, and a small apex area. An adequate level of structural robustness may provide some immunity to the range of tangential or shear forces encountered during normal operation. A small apex cross-section-to-tip-height ratio may assist with the placement of the probe tip and avoid unnecessary contact with ancillary structures surrounding the electrical feature of interest on the semiconductor die (e.g., a contact pad or solder bump). Finally, a small apex area may increase local pressure and ease any required scratching of oxide layers over the electrical structures of interest and facilitate the penetration of metallic surfaces.
In light of these desired design features, a possible probe tip shape that meets these desirable attributes may include a conical or pyramid shape. In other words, a desirable probe tip shape may define a volume with a large base, providing mechanical robustness to shear forces, and a small apex for efficient scratching of metal oxides and penetration of metallic surfaces.
Such conical or pyramid-shaped probe tips may be manufactured utilizing molds. However, such manufacturing methods based upon the use of a defined mold and its subsequent filling (e.g., electro-deposition or electroplating) suffer from limitations pertaining to the types of geometries that can be achieved during the definition of the mold itself, especially when the mold is the result of a photolithographic process. Although photolithographic processes can provide molds of an arbitrary shape and height, they typically yield molds with straight sidewalls, essentially oriented along an axis perpendicular to the surface underneath. Cone, truncated cone, or pyramid shapes are generally more difficult to achieve via photolithography alone.